Effect of different positive end expiratory pressure levels on optic nerve sheath diameter in patients with or without midline shift who are undergoing supratentorial craniotomy.

PURPOSE: In general, high levels of PEEP application is avoided in patients undergoing craniotomy to prevent a rise in ICP. But that approach would increase the risk of secondary brain injury especially in hypoxemic patients. Because the optic nerve sheath is distensible, a rise in ICP is associated with an increase in the optic nerve sheath diameter (ONSD). The cutoff value for elevated ICP assessed by ONSD is between 5.6 and 6.3 mm. We aimed to evaluate the effect of different PEEP levels on ONSD and compare the effect of different PEEP levels in patients with and without intracranial midline shift. METHODS: This prospective observational study was performed in aged 18-70 years, ASA I-III, 80 patients who were undergoing supratentorial craniotomy. After the induction of general anesthesia, the ONSD's were measured by the linear transducer from 3 mm below the globe at PEEP values of 0-5-10 cmH2O. The ONSD were compered between patients with (n = 7) and without midline shift (n = 73) at different PEEP values. RESULTS: The increases in ONSD due to increase in PEEP level were determined (p < 0.001). No difference was found in the comparison of ONSD between patients with and without midline shift in different PEEP values (p = 0.329, 0.535, 0.410 respectively). But application of 10 cmH2O PEEP in patients with a midline shift increased the mean ONSD value to 5.73 mm. This value is roughly 0.1 mm higher than the lower limit of the ONSD cutoff value. CONCLUSIONS: The ONSD in adults undergoing supratentorial tumor craniotomy, PEEP values up to 5 cmH2O, appears not to be associated with an ICP increase; however, the ONSD exceeded the cutoff for increased ICP when a PEEP of 10 cmH2O was applied in patients with midline shift.

Improved optic nerve visualization and treatment planning through a dedicated optic nerve MRI protocol.

OBJECTIVE: This study describes an innovative optic nerve MRI protocol for better delineating optic nerve anatomy from neighboring pathology. METHODS: Twenty-two patients undergoing MRI examination of the optic nerve with the dedicated protocol were identified and included for analysis of imaging, surgical strategy, and outcomes. T2-weighted and fat-suppressed T1-weighted gadolinium-enhanced images were acquired perpendicular and parallel to the long axis of the optic nerve to achieve en face and in-line views along the course of the nerve. RESULTS: Dedicated optic nerve MRI sequences provided enhanced visualization of the nerve, CSF within the nerve sheath, and local pathology. Optic nerve sequences leveraged the "CSF ring" within the optic nerve sheath to create contrast between pathology and normal tissue, highlighting areas of compression. Tumor was readily tracked along the longitudinal axis of the nerve by images obtained parallel to the nerve. The findings augmented treatment planning. CONCLUSIONS: The authors present a dedicated optic nerve MRI protocol that is simple to use and affords improved cross-sectional and longitudinal visualization of the nerve, surrounding CSF, and pathology. This improved visualization enhances radiological evaluation and treatment planning for optic nerve lesions.

Endoscopic endonasal decompression of the optic nerve in the setting of compressive lesions: how I do it.

BACKGROUND: Many lesions in the anterior skull base may compress the optic nerve (ON), leading to vision loss, and even irreversible blindness. Although decompression of the optic nerve has traditionally been achieved transcranially, the endoscopic endonasal approach (EEA) is gaining traction as a minimally invasive approach recently. METHOD: We describe the key steps of an EEA ON decompression. The relevant surgical anatomy with illustration is described. Additionally, a video detailing our technique and instruments on an illustrative case is provided. CONCLUSION: Endoscopic endonasal approach ON decompression with a straight feather blade is a feasible, minimally invasive procedure to decompress the ON in the setting of anterior skull base mass lesions.

Surgical management of pseudotumor cerebri syndrome: A single center experience with endoscopic optic nerve decompression and CSF diversion procedures.

OBJECTIVES: Pseudotumor cerebri syndrome (PTC) is a chronic disorder, which is initially treated by conservative measures, yet surgery is inevitable in case of progressive worsening of vision or headache despite medical treatment. The surgical management is controversial including CSF diversion procedures and optic decompression. The purpose of this study was to evaluate the efficacy of different surgeries in PTC and to present surgical outcomes in a single center. METHODS: This retrospective study included the patients with PTC who were operated by endoscopic optic nerve decompression (EOND), ventriculoperitoneal (VP) and lumboperitoneal (LP) shunting. Surgical outcomes, i.e. visual acuity, visual field, papilledema and headache were compared according to type of surgery. Surgical complications were noted. RESULTS: Seventeen of 36 patients were treated with shunting, 14 with EOND and 5 patients with both EOND and shunting. No statistical significance was observed between CSF diversion procedures and EOND concerning clinical outcomes. The improvement rate of papilledema was higher with VPS (p = 0574) while more patients benefitted from LPS regarding visual field and acuity (p = 0471 and p = 0718, respectively). The best treatment response for headache was in shunt implemented patients (VPS and LPS) with a rate of 88.2% followed by EOND (78.6%) and both surgeries (60%)(p = 0.294). Gender and BMI were significant predictors of improved papilledema (p = 0.034). CONCLUSIONS: Our study demonstrated comparable results between shunting and EOND, regarding the efficacy on surgical outcomes. EOND is quite effective for headache besides its advantage on treatment-refractory visual loss. Shunting may offer sustained relief of symptoms when compared with EOND.

Optic Canal Size is an Indicator for the Accessory Optic Canal: Applications for Anterior Clinoidectomy.

BACKGROUND: The ophthalmic artery normally travels with the optic nerve through the optic canal. However, sometimes, the ophthalmic artery travels through a foramen within the optic strut named an accessory optic canal, double optic canal, or ophthalmic canal. This variant puts individuals at an increased risk for blindness or death during anterior clinoidectomy due to unforeseen hemorrhage of the ophthalmic artery or internal carotid artery when the optic strut is separated from the body of the sphenoid bone. Several features make the accessory optic canal difficult to recognize on imaging: its variant nature, small size, and ability to masquerade as a caroticoclinoid foramen or a pneumatized sphenoidal structure. Hence, improved methods of presurgical identification are warranted. The aim of this study was to assess the size and shape of the optic canal, with and without a concomitant accessory optic canal, to determine whether measurement of the optic canal may provide useful information regarding the presence of an accessory optic canal. METHODS: In 191 dry crania, optic canals with and without concomitant accessory optic canals were assessed for the following parameters: canal area, canal perimeter, circularity, solidity, the axes and aspect ratio of a best-fit ellipse, and roundness. RESULTS: Normal optic canals were found to have a larger area (P = 0.036), perimeter (P = 0.043), and minor axis of a best-fit ellipse (P = 0.031) than the optic canals that occurred alongside accessory optic canals. CONCLUSIONS: Asymmetry in optic canal size can help indicate the presence of a unilateral accessory optic canal before surgery.

Cranioorbital Pretemporal Skull Base Approach with Anterior Clinoidectomy for Removal of Large Left Clinoid Meningioma: "Unwrapping" Encircled Internal Carotid Artery and Decompressing Optic Nerve: 2-Dimensional Operative Video.

Clinoidal meningiomas are meningiomas arising from or in the vicinity of the anterior clinoid process.1 Despite advanced microsurgical techniques, clinoidal meningiomas remain challenging.2 Extradural anterior clinoidectomy with optical unroofing remains an important tool in skull base surgery, which provides a safe operative corridor, facilitating greater extent of resection and enhancing overall outcome, particularly visual function.2-13 A 66-year-old woman presented with history of visual disturbances. Magnetic resonance imaging revealed a dural-based tumor consistent with a large left clinoidal meningioma, with tumor wrapping (encircling) around the left trunk and internal carotid artery (ICA) bifurcation, elevating the left middle cerebral artery M1 segment, and invading the left optic canal. Left cranio-orbital craniotomy with pretemporal exposure was used (Video 1).1,9 A high-speed diamond drill with irrigation completed the extradural anterior clinoidectomy and optical canal unroofing. Use of a 1-mm Kerrison rongeur should be done with utmost care. The tumor was unwrapped via meticulous piecemeal removal. Final dissection and ICA unwrapping was done when the tumor was debulked enough that dissecting it off the artery was safe and under less tension. Due to its obscurity, final decompression of the left optic nerve with incision and opening of the falciform ligament was performed at the end of the procedure.10 Postoperative neuro-ophthalmologic examination showed a grossly unchanged left visual field with some visual acuity improvement. Resection of tumor encircling the ICA has been described previously;14 however, to the best of our knowledge, this is the first video describing removal of a tumor surrounding the ICA (perfomed by senior author K.I.A.), essentially "unwrapping" the left ICA trunk and its bifurcation. The patient consented to publication.

Visual Outcomes Following Surgical Debulking in Exophytic Optic Nerve Sheath Meningiomas.

PURPOSE: To report a case of a globular primary optic nerve sheath meningioma managed surgically with improvement in vision and review the literature for outcomes of purely intraorbital exophytic-globular primary optic nerve sheath meningiomas managed surgically. METHODS: A literature review was conducted using Google Scholar and PubMed with the search terms "primary optic nerve sheath meningioma," "surgery," "exophytic," and "globular." Articles were included if they were available in English. Individual cases from the reviewed articles were included if the tumor was purely intraorbital with a globular or exophytic morphology, was managed with total or subtotal surgical excision, and visual outcomes were reported. Cases were excluded if the tumor extended intracanalicularly or intracranially, tumor morphology was unknown, or surgical management consisted of biopsy, optic nerve sheath decompression, or optic canal decompression rather than tumor debulking. RESULTS: A total of 28 patients with intraorbital globular-exophytic primary optic nerve sheath meningiomas managed surgically have been reported in the literature. Vision improved in 29% (n = 8/28) and remained stable in 43% (n = 12/28) of patients. Furthermore, patients with good (Snellen notation ≥ 0.5) vision (n = 10) typically retained good vision postoperatively and at follow-up, with 1 patient experiencing a decline to poor (Snellen ≤0.1) vision at the last follow-up (92 months postoperatively). Similarly, patients with fair (Snellen notation >0.1 and <0.5) vision (n = 5) often improved to good vision (n = 3) or stayed at fair vision (n = 1), with 1 declining to poor vision at postoperative hospital discharge. CONCLUSIONS: Surgical management of exophytic or globular optic nerve meningiomas does not universally lead to vision loss and may be appropriate in select patients.

Comparison of extraperitoneal and intraperitoneal laparoscopic procedures for intracranial pressure increase: a prospective clinical study.

OBJECTIVE: According to the literature, higher levels of both intracranial pressure (ICP) and intraabdominal pressure (IAP) are related in a way that suggests a causal relationship. An increase in ICP can cause major neurological problems both during and after laparoscopic surgery. In this study, we aimed to examine the increase in ICP between totally extraperitoneal (TEP) inguinal hernia repair and laparoscopic cholecystectomy. PATIENTS AND METHODS: We investigated 52 individuals who underwent laparoscopic surgery for the treatment of inguinal hernia (n = 26) or had a laparoscopic cholecystectomy (n = 26). The optic nerve sheath diameter (ONSD) was assessed before the procedure (T0), 10 minutes after carbon dioxide insufflation (T1), and immediately before extubation (T2). RESULTS: There were significant differences in the ONSD values between the two groups as a function of time (p = 0.001). In terms of ONSD, the laparoscopic cholecystectomy value (LV) group showed a greater shift from T0 to T1 and T2 than the inguinal hernia value (HV) group. At T1, the ONSD values of both groups were considerably higher than those of T0 and T2. The impact of the extraperitoneal and transperitoneal laparoscopic methods on ICP was investigated. The ONSD value reached its maximum at T1 in both groups. At all measurement periods, the ONSD values of the LV group were noticeably higher than those of the HV group. CONCLUSIONS: The diagnostic accuracy of ONSD ultrasonography is an important approach for determining the ICP level. During the decision-making process of TEP inguinal hernia repair, this study can guide medical professionals in the evaluation of elevated ICP.

Optic nerve sheath fenestration: A second lease at sight.

Purpose: To study the safety and efficacy of optic nerve sheath fenestration surgery in patients with optic disc edema due to different etiologies. Methods: Records of 18 eyes of 15 patients who underwent optic nerve sheath fenestration for vision threatening optic disc edema were reviewed retrospectively, and results were analyzed. Improvement of visual acuity was the main measure of outcome. Improved visual fields, resolution of optic disc edema, diplopia, and headache were other benefits that were observed. Results: Fifteen patients between 13 and 54 years of age were included in the study. Three patients underwent successive bilateral surgery. Idiopathic intracranial hypertension was the most common cause for optic disc edema and was found in 80% of the patients. Mean preoperative logMAR acuity was -1.9789 ± 1.46270, which improved to -0.9022 ± 1.23181 (p < 0.005) in the operated eye, and mean logMAR acuity of contralateral eye improved from -1.3378 ± 1.50107 to -1.0667 ± 1.33813 (p < 0.05). Conclusion: Early optic nerve sheath fenestration is an effective modality for treating optic disc edema due to a wide myriad of causes and helps resolve the associated symptoms.

Endoscopic Endonasal Optic Nerve Decompression in Idiopathic Intracranial Hypertension: When to Implement Optic Nerve Sheath Fenestration.

BACKGROUND AND OBJECTIVE: Idiopathic intracranial hypertension (IIH) is a syndrome characterized with increased intracranial pressure and normal cerebrospinal fluid (CSF) composition. Treatment is mainly conservative, whereas CSF diversion surgery is the most frequently used surgical intervention. Endoscopic endonasal optic nerve decompression (EOND) is a newer surgical treatment of this patient group. This study presents a single clinic's case series with comparative results of unilateral an bilateral EOND with or without optic nerve fenestration. METHODS: Sixteen patients with IIH syndrome who underwent 18 EOND procedures by a single neurosurgeon were evaluated with MRI and digitally subtracted angiography preoperatively. Both preoperative and postoperative visual acuity and perimetry and fundoscopy examinations were routinely performed. All patients underwent sphenoidotomy using the endoscopic binostril approach; however, unilateral or bilateral optic nerve decompression and accompanying optic sheath fenestration was determined on a case-by-case basis, after which all patients were also evaluated for the outcome of headaches. RESULTS: Most of the patients were female, and the mean age was 30.28 ± 9.78 years. CSF pressure was increased in all patients (406.43 ± 112.91 mm of H 2 O), and the follow-up period was 61.72 ± 21.67 months. In patients with unilateral EOND, visual fields improved in 83%, visual acuity in 70%, headache in 75%, and papilledema in 27% of cases. In patients with bilateral EOND, perimetry improved in 86%, visual acuity in 43%, headache in 50%, and papilledema in 57% of cases. CONCLUSION: EOND is an effective surgical option in the treatment of IIH. Bilateral decompression is preferable in patients with bilateral visual involvement, and optic nerve fenestration may prove to be helpful in patients with IIH whose primary complaint is headache.

Endoscopic endonasal optic nerve sheath decompression (EONSD) for idiopathic intracranial hypertension: Technical details and meta-analysis.

BACKGROUND: The neurosurgical management of idiopathic intracranial hypertension (IIH) remains controversial. Although shunting and newer endovascular stenting techniques are part of the neurosurgical armamentarium to treat medically refractory IIH symptoms, optic nerve sheath fenestration has traditionally been performed by ophthalmologists. OBJECTIVE: We present a detailed cadaveric dissection that simulates the endoscopic endonasal optic nerve sheath decompression (EONSD) technique along with the literature review. METHODS: EONSD was performed in four freshly injected cadaveric specimens. Additionally, a systematic review from different electronic databases has been done. RESULTS: Bilateral EONSD was performed in all specimens without significant technical difficulties. Based on our experience, there is no need to expose the periorbita or orbital apex. The primary anatomic landmarks were the optic canal, the lateral opticocarotid recess, the tuberculum, the limbus, and the clinoid segment of the internal carotid artery. Based on the systematic review, 68 patients (77.9% female) underwent EONSD, with a mean age of 33.4 ± 6.9 years in adult patients. Follow-up ranged from 3 to 58 months across different studies. The pooled meta-analysis showed headache, papilledema, and visual disturbance improvement in 78% [95%CI 0.65-0.90], 72% [95%CI 0.61-0.83], and 88% [95%CI 0.80-0.96] of cases who underwent EONSD, respectively. The subgroup analysis showed there was no statistically significant difference between unilateral and bilateral EONSD in terms of different measured outcomes. CONCLUSION: EONSD is a feasible surgical procedure that may obviate the need for shunting in patients with IIH. Although clinical studies showed that EONSD is a safe and effective technique, further studies are required to establish the preferences of either unilateral or bilateral approaches.

Anatomical Study and Clinical Application of Optic Canal Decompression Via Transethmoid-sphenoid Approach Under Endoscope.

This study aimed to evaluate the safety and accuracy of the endoscopic transethmoid-sphenoid approach for optic canal decompression. Twelve sides of 6 adult cadaveric heads fixed in formalin were selected to simulate optic canal decompression using the endoscopic transethmoid-sphenoid approach. Furthermore, this approach was used for optic canal decompression in 10 patients (11 eyes) with optic nerve canal injury. Related anatomical structures were observed using a 0-degree endoscope, and the anatomical characteristics as well as the surgical data were collected. The maximum effective widths of the cranial opening, orbital opening, and middle segment of the canal that could be drilled open endoscopically were 7.82±2.63, 8.05±2.77, and 6.92±2.01 mm, respectively. The angle between the line linking the center point of the tubercular recess with the midpoint of the cranial opening of the optic canal and the horizontal coordinate was 17.23±1.34 degrees. At the orbital opening of the optic canal, the ophthalmic artery was located directly inferior to the optic nerve in 2 cases (16.7%) and laterally inferior to the optic nerve in 10 cases (83.3%). Six of the operational eyes were effective while the remaining 5 were ineffective. No postoperative complications such as bleeding, infection, or cerebrospinal fluid leakage were observed during the follow-up period (6-12 mo). In conclusion, optic canal decompression positively impacts the prognosis of partial traumatic optic neuropathy. Furthermore, the endoscopic transethmoid-sphenoid approach for optic canal decompression is a minimally invasive procedure that provides direct access and adequate decompression. This technique is easy to master and suitable for clinical applications.

Alternative Path for Optic Nerve Decompression in Pseudotumor Cerebri With Full Endoscopic Lateral Transorbital Approach.

Endonasal endoscopic approaches are the most preferred surgical methods in patients with pseudotumor cerebri because of easy access to the optic nerve, but the choice of this technique may not apply to all endoscopic endonasal cases. Moreover, there may be difficulties in practice in some cases, including the coronavirus disease 2019 pandemic. This study aimed to suggest an alternative endoscopic approach by lateral orbitotomy for optic nerve decompression in patients with pseudotumor cerebri. The study was performed using 5 fresh-frozen cadaver heads (bilaterally, total of 10 sides) injected intravenously with colored silicone preserved in the cold chain. An average of 2.5 cm skin incision was made to fit the lateral orbitotomy. The lengths of the recurrent meningeal artery (mm), the meningo-orbital band (mm), and the optic nerve (mm) to the orbital margin were measured. After these morphometric measurements, optic nerve decompression was performed endoscopically, and the length of the decompression was measured (mm). The average length (mm) between the orbital rim and meningeal recurrent artery (or meningolacrimal branch) was 16.2 mm, between the orbital rim and the meningo-orbital band was 18.5 mm, and between the orbital rim and optic nerve was 44.1 mm. The average optic nerve decompression length was 4.4 mm. The endoscopic lateral orbitotomy approach provides easy access to the optic nerve by anatomically following the recurrent meningeal artery and the meningo-orbital band. It can be a safe second-line approach after endonasal approaches for optic nerve decompression in pseudotumor cerebri.

Optic nerve sheath diameter as a quantitative parameter associated with the outcome in patients with traumatic brain injury undergoing hematoma removal.

PURPOSE: To determine the association between optic nerve sheath diameter (ONSD) and outcome in patients with traumatic brain injury (TBI) who undergo hematoma removal (HR). METHODS: This study was a retrospective analysis of data from a single center between 2016 and 2021. Adult patients with TBI who underwent HR within 24 h after admission were included in this study. Preoperative and postoperative ONSD of the surgical side and the mean ONSD of both sides were measured for analysis. The primary outcome was mortality at 30 days. Receiver operating characteristic curve analysis was performed to calculate the area under the curve (AUC) and 95% confidence interval (CI) for 30 days mortality. RESULTS: Sixty-one patients were enrolled in the study. Among them, 48 (78.7%) survived for 30 days after admission. The AUC and 95% CI of the postoperative mean ONSD on both sides and postoperative/preoperative mean of the ONSD ratio on both sides were 0.884 [0.734-0.955] and 0.875 [0.751-0.942], respectively. The postoperative mean of both ONSDs of 6.0 mm had high accuracy as a cut-off value with a sensitivity of 85%, specificity of 83%, positive likelihood ratio (LR) of 5.0, and negative LR- of 0.18. CONCLUSION: This study demonstrated that postoperative ONSD and the postoperative/preoperative ONSD ratio were associated with postoperative outcome in patients with TBI who underwent HR.

Cisternal, Falciform, and Optic Canal Decompression Influencing Optic Nerve Biomechanics: A Microsurgical Anatomic Study.

BACKGROUND: Questions remain regarding optic nerve (ON) physiology, mechanical compliance, and microvasculature, particularly surgical outcomes and atypical visual field defects associated with sellar/parasellar pathology (eg, tumors and aneurysms). OBJECTIVE: To study the microsurgical/histological anatomy of each ON segment and corresponding microvasculature, calculate area of optic-carotid space at each decompression stage, and measure ON tension before/after compression. METHODS: Five cadaveric heads (10 sides) underwent sequential dissection: (1) intradural (arachnoidal) ON dissection; (2) falciform ligament opening; (3) anterior clinoidectomy, optic canal decompression, and ON sheath release. At each step, we pulled the nerve superiorly/laterally with a force meter and measured maximal mobility/mechanical tension in each position. RESULTS: Cisternal ON microvasculature was more superficial and less dense vs the orbital segment. ON tension was significantly lower with higher mobility when manipulated superiorly vs lateromedially. Optic-carotid space significantly increased in size at each decompression stage and with ON mobilization both superiorly and laterally, but the increase was statistically significant in favor of upward mobilization. At decompression step, upward pull provided more space with less tension vs side pull. For upward pull, each step of decompression provided added space as did side pull. CONCLUSION: Opening the optic canal, falciform ligament, and arachnoid membrane decompresses the ON for safer manipulation and provided a wider optic-carotid surgical corridor to access sellar/parasellar pathology. When tailoring decompression, the ON should be manipulated superiorly rather than lateromedially, which may guide surgical technique, help prevent intraoperative visual deterioration, facilitate postoperative visual improvement, and help understand preoperative visual field deficits based on mechanical factors.